Process of producing nitric oxid from mixtures of nitrogen and oxygen and apparatus therefor.



- Patented May 2, 1911.

INVENTOR:

HARRY PAULING oo 00 .0 oooo k o o H. PAULING.

APPARATUS THEREFOR. AFPLIGATION FILED SEPT. 27, 1910.

WITNESSES toma-ry to heat gaseous mixtures comprising nitrogen and oxygen, commonly by means gases mshamanismcontaining more or less ofth'e oxide. The processes heretotendency for nitrogen and oxygen to com- 1 ct'ivelyliiglr temperatures becomes quite great less intot cfree; nitrogen and oxygen. 7 But at:

,sive and of relatively low efficiency At UNITED srat rs PATENT onFIoE;

mam? manner, or :GELSENKIRCHEN, GERMANY, Assronoa r0 sanrmnnsaunn- IND'U'sTRIE-qEsELLscHAF'r, GESELLSCHAFT M'rr nnscnmm'zrnn HArTUnG, or

eersenxmcsnn, Gummy enemies or rnon'ucnm marine oxrn FROM MIXTURES or NITROGEN ANn-oxY'eEn APPARATUS 'ILHEREFOR.

i Specification was Patent.

Application filed September 27,1910. Serial No. 584,121.

To all whomit may concern:

Be, it known that LliARRY' PAULIxG,manager; a subject of the-King of'Saxony, residing at 84 \Vilhelmstras'se, Gelscnkirchen IV, in the Kin'gdonr of Prussia, ermanE'mpire. riave invented a new and" useful Improve-- ment in Processes of Producing Nitric Oxid from Mixtures of Nitrogen and Oxygen and Apparatus therefor; and I- do hereby declare .the following to be a full, clear, and exact description of thesame.

This invention relates to processes of treating gases and apparatus therefor; and it comprises a process wherein a gaseous mixture,-specificallya mixture comprising nitrogen and oxygen, is heated toa reacting tem? 'perature', is thereafter permittedto expand without material reduction in temperature, additional heat being supplied I if desired during suchexpansion, and is finally-cooled; and,it"also comprises apparatus suitable'for carrying out the foregoing process compris ing a reactionfurnace, an expansion chamber in communication with said furnace, means for permitting expansion of'h'otgases from said furnace into said reaction chamber Without cooling 'during such expansion, special he'ating means being provided if de sired, and means for cooling the hot expanded gasm; all: as more fully-hereinafter set forth and as claimed.

3 Inmproducing oxidsof nitrogen, it is cus obtained'in the electric 'arc for example, this backward tendency of the reaction is com- 'composition of the oxids. And at temperature considerably below that of the arcrthere is also relatively little tendency towarddecomposition of the oxids. I mediate temperature however, when the sysamount of uncombined nitrogen and oxygen on one side of the reactionequation, as well asa definite amount of nitrogen oxids on the other side. And at the same time the x'elocity ofthe' decomposing reaction is very high. Obviously therefore it would beexceedingly advantageous if-the extremely hot gaseous mixture high in-oxids "of nitrogen coming from the are could be treated in such a manner that its temperaturewouldbe reduced to a vpoint at which there is substantially no tendency for the oxids to decompose, without at the same time encountering the unfavorable condition-s existing. in the intermediate range of temperatures above referred to. Attempts have heretofore been made to accomplish uns end by suddenly the arc through a cooled pipe in wh chthe the'decomposition of oxids incident to temperatures between that of the arc and those 'ofau electric arc, to a temperature suflicientl'y. high: to bring about the desired vrea 'ction ,-and then to cool the hot reaction of temperatures as rapidly as possiblm For "relatively unsuccessful. In the first place, fore employed" however have proved expenthe speed of cooling, e'ven'under the most ordinary'temperatures thereis very little small as compared with thej'speed' of, the

bine', the reaction, if any,'being so slowns togbeflpractically imperceptible With 1ncrease n temperature however, the speed of the ,.re'act=io1 i' ncreases rapidly, and at rela high temperatures necessarily passed over during thefcoohng. Consequently it 1511111 tions}. heretofore proposed with, sufficient speed to a oid ve1'y considerable decompo: sition ofthe oxids duringthe cooling step. The formation'of oxid's 1s anendothermic reaction ofgases; that isg'it is a'heat-consum- -.ing-reaction and is subjectto' the gsame laws as; "other reactions of the same, nature;

At all temperatures at which nitrogen and oxygenreact with each other, the reaction is reversible to a 're ater or less extent; 2'; a the 'oxids formed tend to decompose more 1" Patented Mil-y 2,1911.

Y paratively small; the reaction proceeds forward almost entirely, and there is little detem is in equilibrium, there is a considerable cooling the gases by drawing the from' gaseous'mixture is subjected to a suddendrop n temperature) the idea 'belng to avoid several, reasons, these attempts have beenfavorableconditions, is relatively extremely retrogressive ordecomposing reaction at the possible to cool the gases under the condi exceedingly high temperatures, such as are -At any in'terat which there is practically no decomposition, by passing over tlnsdangerous range,

- 5. he object of Furthermore in coolin the aseous-inixturel in the manner descri d, t e are itself is also cooled, and of course this is disadvan decomposition speed of the gases, before the cooling process, and the novelfeaturcof the v..improved process consists substantially in subjecting the heated mixture to expansion wthout materially reducing its. temperature during such expansion. For this purpose the heated mixture may be introduced into a chamber in which the pressure is reduced to about 400 -mm.'mercur'y, this chamber beingheated if necessary to maintain the'tein-' perature of the mixture during the expansion of the latter therein. After the expan- 'sion, the gases are cooled. The reaction velocity is greatly reduced by the expansion, being under the present conditions probably approximately proportional to the square of the pressure. On the other hand, the reaction equilibrium is practically undisturbed since the temperature is not allowed todrop during the expansion. Consequently the proportions of nitrogen oxids produced by the reaction at the highest temperatures are maintained substantially. constant duringl T30 the subsequent cooling, theresulting coole gaseous mixture being substantiallya's rich in oxids. of nitrogen as the intensely liot mixture at. the electrodes.- A

:In applying my new processto the manufact'ure of nitrogen oxids -where gaseous mixtures containing. nitrogen and oxygen are subjected to the action of'an electric are,

1 find it best to form the arc and introduce the. gases thereinto at approximately'no'rnial After treatment in the arc, the intensely hot gases are then permitted to expand into a chamber in which .a partial yacuum is maintained, without material re duction in their tem eratureq Reduction in the-temperature of t e hot gases may berevented either by supplying additional eat to the gases .during the expansion, or by.

{throttling their flow into the expansion 'chaniber.- The pressure in the expansion ,chaiiiber should be relativelylow, and for the best results should not be .over 400-millimeters oat -mercury. Still lower pressures are even better. y

Various-methods may be. used for heating during the expansion. One method consists in introduci'rig'a suitable proportion of com- 'bustible gas intothe stream of intensely-h 0t,

expanding mixture gen), so that combustiontakes place and compensates for the fall of tem' erature due to expansion. The amount 0 added gas need only be-in,s uch pro portion as to consums it very small amount of the available oxygen. Or a flame are between .waterthe present invention is to "obviate these disadvantages by reducing the which, as is known, must contain a consi erable excess of oxycooled platinum electrodes or the like may be placed in the chamber or the latter may be heated by means of heating conduits in its walls. It is, in practice, well to main.- tain the gases during the expansion at a temperature of about 2,0.00 G. Among other materials, magnesia is capable of resisting this temperature, and is suitable for the walls of the expansion chamber.

One of the many forms of apparatus suit able for the purpose of the invention is diagran'imatically illustrated in the annexed drawing, which is a sectional view. -In the type of apparatus here shown, drop in term perature of the expanding gases is prevented by throttling their flow into the ex pansion chamber.

chamber or furnace, to which the air or other mixture of nitrogen and oxygen is supplied through the pipe 2, and whence the reaction mixture resulting from the action of the are or other heating means (not shown),

- passes through the ,fiared'duct 4 to the vacuvery constricted so as to give the desired,

throttling eifect. If the heat from the chamber 1 is'not suflicient to maintain the requisite temperature in the chamber 3, the

latter may be heated by means of heating conduits or equivalent means (not known),

to'preventfall of temperature durin the expansion. In the type of apparatus 's own, supplementalheating means are not usually necessary unless the expansion chamber is at such a distance from the, furnace that radiation losses become excessive; A pump 6 connected to the chamber 3 b a pipe 5, serves to maintain the desired egree of reduced pressure in the expansion chamber.

temperature during expansion in order to prevent material decomposition of the reaction products.

2' The rocess of producing oxids of nitrogen, w ich comprises forming oxids of nitrogen by heating a gaseous mixture comprising nitrogen and oxygen to a reacting temperature, and then permitting such heated mixture to expand withoutsubstantial reduction in temperature during. expansion.

3. The rocess of producing oxids of nitrogen,-'w ich comprises heating a gaseous mixture comprising nitrogen and oxygen to a reacting .tem 'aeature, permitting such heated mixture toexpand while maintaining the ten'iperature above that at which mate' rial decomposition of said oxids' occurs, and

subsequently coolin the expanded. mixture. 41. The process of producing oxids ofnitrogen, which comprises sub]ecting' a gas- 'cous mixture comprising nitrogen and oxyto gen to the heating action of an arc to form oxids of lntrogen, and perm tting a thrdt-J .tled expansion of the resulting hot gaseous mixture without materlal reduction-1n tem- 'peratu're during such expansion.

.3. The 'process of producing 'OXldS of'ni trogen, which comprises subjecting a gaseous mixture comprising nitrogen and oxygen to the heating action of an arc, permitting a throttledexpansion of the resulting hotgaseous mixture without material re'ductionjn temperature, and thereafter cooling the expanded gases to a temperature below thatat which material decomposition of nitrogen oxids occurs. v V v f G. The'process of producing ,oxids of nitrogei'i. which comprises forming oxids of nitrogen by heating a gaseous mixture comprising nitrogen. and oxygen to a reacting temperature. and then permitting the heated mixture to expand under reduced pressure ,Wltlltlllt material reduction in temperature during the expansion.

T. The process of prodpcmg oxide of n1- tro-gen, which cmnprises heating a gaseous mixture comprising mtrogen and oxygen to a reacting temperature, permitting the heated mixture to expand under reduced pressuredwithout material 'ejduction in 'tem .p'nrature during the expan ion', and thereaf- 40 terirooling the hot expanded mixture.

, .firThe process of producing oxids of nitrogen, which comprises passing a mixture comprising nitrogen'and oxygen through an arci'tofprin oxide of nitrogen, permitting the resulting hot gaseous mixture to expand substantially .isothermall'y through a constricted passage into anexpansion chamber in which a partial vacuum is maintained,

and thereafter. cooling the, expandedmix .ture. t v. 9.. In'apparatus for making oxids of nitrogen, means for heating mixed gases comprising ,nitrogenjand oxygen toreacting temperature, in comblnatlon withmeans for 1 permitting 'hot gases from said. heating means to expand without reduction in temperature during the expansion.

'10. In apparatus for-treating gases, means for heating mixed gases to a reactin Itemperature, andmeans fpr permitting t 1e hot reaction gases from said heating means to expand without material reduction in temperature. V

I 11. In apparatus fortreating gases, means for heating mixed gases to .a reacting tem' pe'rature, means for. permitting the hot reaction gases from said heating means to ex; 'pand without material reduct on in temperature, and .means connected to'sald expan- Dated this twelfth day of September 1910.

Intestimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

HARRY PAULING.'

itnesses MATHILDE' K. HELD, A. V... W. COTTER. 

